[www-scripts] Clang Attribute Doc Update: ERROR

[root via www-scripts]

UPDATING LLVM SOURCES
HEAD is now at d889e17 [SimpleLoopUnswitch] Drop make.implicit metadata in case of non-trivial unswitching
>From https://github.com/llvm/llvm-project
 * branch            master     -> FETCH_HEAD
   d889e17..30a0dbb  master     -> origin/master
First, rewinding head to replay your work on top of it...
Fast-forwarded master to 30a0dbb70d9e0c94a9bdc3d28e7c1c57d9891912.
CMake Error at CMakeLists.txt:3 (cmake_minimum_required):
  CMake 3.13.4 or higher is required.  You are running version 3.7.1


-- Configuring incomplete, errors occurred!